FIG. 1 is a diagram showing the configuration of a prior art three-dimensional measurement system using an IGPS. Referring to FIG. 1, the three-dimensional measurement system using an IGPS includes a scale bar 10, a vector bar 20, a plurality of optical transmitters 30a and 30b, and a receiver 40.
The receiver 40 is attached to the vector bar 20, and one end of the vector bar 20 is sharp to come into contact with the scale bar 10 in vertical during measurement. The receiver 40 receives electric waves and laser beams radiated from at least three optical transmitters 30a and 30b. At this time, the measurement is performed by moving the receiver 40 between two known positions. In the three-dimensional measurement system, measured coordinates of the positions are converted into a distance between the two positions, to thereby measure the distance between the two positions.
In the above-described three-dimensional measurement system using an IGPS, when the vector bar 20 indicates a point on the scale bar 10, a worker needs to use his/her hands to directly indicate the point. However, it is difficult for the worker to accurately indicate the point. Accordingly, a measurement value of the point may vary each time the measurement is performed. In addition, an error due to this problem may cause a cumulative error, and thus, when a distance between two positions is measured, the distance may be measured to be larger than an actual distance.